On Monday evening, 49ers linebacker Chris Borland announced his retirement after just one (stellar) season. The 2014 third-rounder out of Wisconsin says concerns over concussions and their longterm effects drove him to the decision.

Borland is the latest, but youngest, in a string of prominent players who recently decided to retire at 30 years old or younger, including Patrick Willis, Jake Locker, Maurice Jones-Drew, and Jason Worilds.

Here's some of what's been said/written/tweeted since Borland's announcement:

Linebacker Chris Borland, the Niners' third-round pick in 2014, and a rising star who notched 107 tackles as a rookie, announced his retirement on Monday. The reason? Fear of concussions, brain injuries, neurodegenerative disease, and early death. As Borland tells Outside the Lines:

I just honestly want to do what's best for my health. From what I've researched and what I've experienced, I don't think it's worth the risk.

Linebacker Nate Irving met with the Colts on Monday but has not yet agreed to a deal with them, according to Josina Anderson. Irving visited with Arizona sometime last week. Last month, Mike Klis reported that the Broncos would attempt to re-sign their 2011 third-rouner.

Prior to free agency, Anderson had reported that Irving was drawing widespread interest from around the league, which suggested he might leave Denver for a better shot at a starting job. But as with the Broncos, Irving wouldn't figure to start for Indy.

One of John Elway's first draft decisions was to take offensive right tackle Orlando Franklin 46th overall in 2011. One of the key stated reasons, repeated several times, was that Franklin brought nastiness to his run blocking. It was contagious, and it helped the whole line. His later-developing skills in pass blocking were often missed. It was a testament to how effective his run-mauling was.

That’s one of the factors for whichever team takes on Florida's D.J. Humphries next month. Humphries has shown himself to be one of the toughest tackles in this year’s draft. He measured in at 6'5" and 307 lb. at the combine - those are pretty standard measurements for tackles. Most years, someone will argue whether arm length matters. If you think it does, his is 33 5/8 inches.

The Broncos agreed to a two-year deal worth a reported $5.65M with free agent guard Shelley Smith (6-4, 310) on Friday. Smith turns 28 in May and figures to replace left guard Orlando Franklin, who signed with San Diego earlier in the week.

A native of Phoenix, Smith was drafted out of CSU in the sixth round of the 2010 Draft by Gary Kubiak's Texans. He spent two years in Houston, but never dressed.

The Broncos have agreed to a two-year deal with Darian Stewart, who is expected to replace Rahim Moore as their starting free safety. Financial terms have not yet been reported.

Stewart (5-11, 214) made $1.3M on a one-year contract with Baltimore last season. He started 14 regular season games (782 snaps, plus-3.0) for them and two more in the postseason (117 snaps, plus-4.0), and will turn 27 in August.

Every new coach brings along a few players and coaches that he trusts. He trusts them to do their job, but knows that it goes both ways. Jack Del Rio was the fire under Terrance Knighton, who turned into a leader.

Owen Daniels has spent all nine of his NFL seasons under Gary Kubiak. They were together for eight years in Houston before spending 2014 in Baltimore. They have a relationship of trust. Every new head coach needs a guy to help teach and motivate the other players at his position. Kubiak feels he can count on Daniels to help fill that role for him.

Daniels came out of the University of Wisconsin in 2006. He’s played in the full zone blocking scheme in both college and in the pros. He was drafted in the fourth round of the 2006 Draft, 98th overall. Kubiak found in him a dependable, intelligent, and focused player.